The concept of disjunct eddy sampling (DES) for use in measuring
ecosystem-level micrometeorological fluxes is re-examined. The governing
equations are discussed as well as other practical considerations and
guidelines concerning this sampling method as it is applied to either the
disjunct eddy covariance (DEC) or disjunct eddy accumulation (DEA)
techniques. A disjunct eddy sampling system was constructed that could
either be combined with relatively slow sensors (response time of 2 to 40 s)
to measure fluxes using DEC, or could also be used to accumulate samples in
stable reservoirs for later laboratory analysis (DEA technique). Both the
DEC and DEA modes of this sampler were tested against conventional eddy
covariance (EC) for fluxes of either CO<sub>2</sub> (DEC) or isoprene (DEA). Good
agreement in both modes was observed relative to the EC systems. However,
the uncertainty in a single DEA flux measurement was considerable (~40%)
due to both the reduced statistical sampling and the analytical
precision of the concentration difference measurements. We have also
re-investigated the effects of nonzero mean vertical wind velocity on
accumulation techniques as it relates to our DEA measurements. Despite the
higher uncertainty, disjunct eddy sampling can provide an alternative
technique to eddy covariance for determining ecosystem-level fluxes for
species where fast sensors do not currently exist.